He was credited with developing the detailed Mortal Kombat storylines and designing its classic characters. Following its arcade debut in 1992, the MKmedia franchise exploded into an overwhelming phenomenon and merchandising bonanza, spawning a host of additional games, as well as two movies, toy and apparel lines, a comic book series, and a 1996 live tour, among others.

By the end of the 1990s, however, the MK series, due to a few disappointing releases and the ill-received 1997 film Annihilation (the sequel to the successful 1995 original), hit a low ebb. John Tobias, along with other prominent Midway staff members such as Dave Michicich and Josh Tsui, left Midway in 1999 and formed Studio Gigante in 2000.